Polyurethanes are typically made by reacting a polyisocyanate compound with a polyol in the presence of an organometallic catalyst. Catalysts for polyurethane manufacture are conventionally based on tin compounds such as dibutyl tin dilaurate or compositions of mercury such as phenyl mercuric neodecanoate. More recently, compounds based upon metals such as titanium or nickel have been used.
Compounds of titanium, zirconium, hafnium, iron (III), cobalt (III) or aluminium were described in WO2004/044027. Such compounds are of general formula RO-M(L1)x(L2)y(L3)z where R is alkyl or a hydroxy-alkyl, hydroxyalkoxyalkyl, or (hydroxy)polyoxyalkyl group and up to 2 of L1 to L3 may represent an amide of acetoacetic acid. These compounds have a single labile —OR ligand and were believed to function as a cure catalyst by exchange or insertion of the polyol or of the isocyanate at the labile site on the organometallic composition, by displacement of the OR group.
U.S. Pat. No. 5,846,897 discloses zirconium compounds with diketones or alkylacetoacetates which catalyse the isocyanate—alcohol reaction having the chemical structure: Me (X1, X2, X3, X4) wherein Me is zirconium (Zr) or hafnium (Hf) and X1, X2, X3, and X4, are the same or different and selected from the group consisting of a diketone and an alkylacetoacetate having the structures: R1COCH2COR2 and R1OCOCH2COR2 wherein each of R1 and R2 is a branched or linear C1-C20 hydrocarbon and at least one of X1, X2, X3, and X4 is a diketone with structure (II) wherein the total number of carbons in R1+R2 is at least 4. Patil et al (J. Mater Chem 2003, 13, 2177-2184) have used zirconium bis(isopropoxide)bis(N,N-diethylacetoacetamide) as a precursor for the metal-organic chemical vapour deposition of zirconium dioxide.
It is an object of the invention to provide an alternative catalyst for making polyurethanes.